const arr = ['1', '2', '3', NaN, null];
console.log('arr.indexOf 2', arr.indexOf('2'));
console.log('arr.indexOf 5', arr.indexOf('5'));
console.log('arr.indexOf NaN', arr.indexOf(NaN));

console.log('arr.includes NaN', arr.includes(NaN));

console.log('2的10次 Math.pow(2, 10)', Math.pow(2, 10));
console.log('2的10次 2 ** 10', 2 ** 10);